JSFiddle - React, Tailwind, and code Playground

HTML

<div class="container">
    <div id="menu">
        <ul>
            <li><a href="">Accueil</a><span></span></li>
            <li><a href="">Portfolio</a><span></span></li>
            <li><a href="">Contact</a><span></span></li>
            <li><a href="">A propos</a><span></span></li>
        </ul>
    </div>
</div>

CSS

.clear{height:1%}
.clear:after {
	content:".";
	height:0;
	line-height:0;
	display:block;
	visibility:hidden;
	clear:both;
}
.container{
    margin: 0 auto;
    width:1200px;
    height:0;
}
.blue_solid{
    border-bottom:6px solid #0da6d2;
    margin: 0;
    -webkit-box-shadow: 1px 1px 1px black;
    -moz-box-shadow: 1px 1px 1px black;
    box-shadow: 2px 2px 3px black;
    width:1200px;
}
#menu{
    font-family: Microsoft Yi Baiti;
    text-transform: uppercase;
    font-size: 20px;
}
#menu a {
    text-decoration: none;
    margin:0;
    padding:0;
    color:#0da6d2;
    border-bottom:5px solid #0da6d2 ;
}
#menu a:hover {
    text-decoration: none;
    color:#667073;
    border-bottom:5px solid #667073;
}
#menu ul{
     
}
#menu li{
    float:left;
    margin:35px 80px 0 0 ;
    list-style-type:none;
    position: relative;
    height:20px;
}

#menu li a span {
    width: 25px;
    margin: 0 auto;
}

#menu li a:hover:after {
    border-left: solid transparent 10px;
    border-right: solid transparent 10px;
    border-top: solid #667073 11px;
    bottom: -16px;
    content: " ";
    height: 0;
    left: 50%;
    margin-left: -13px;
    position: absolute;
    width: 0;
}